The present invention relates to tablets, and in particular it relates to tablets which include a diluent material.
Tablets are conventionally made by moulding or compressing ingredients, and form a suitable means for delivery of an active ingredient, pharmaceutical or otherwise. There is also a large market for sweets in the form of tablets containing flavouring material as active ingredients.
In order to produce tablets, it is necessary to have a free-flowing material which has good self-binding properties and which will not stick to the moulding or compression equipment. Such properties are obtained by using diluents and one or more additives, for example binders and/or lubricants, and by controlled granulation of the ingredients. Some diluents of themselves possess binding and/or lubricating properties, but normally will require careful granulation.
Lactose is a commonly used diluent, having an acceptable taste. However, lactose alone has little adhesive property and normally requires the use of a binder. Moreover, moist granulation is usually needed, involving wetting of the ingredients to give a moist, coherent powder, then sieving, and controlled drying to give granules suitable for preparation of tabletting powders.
Sucrose, particularly sucrose of small particle size, is also a suitable diluent. Moist granulation is usual, unless one employs the specially formulated tabletting materials such as `Di-Pac`, a blend of maltodextrin and sucrose produced by Amstar Corporation of the United States of America using a microcrystallization process.
Other diluents are in use, for instance, starch, glucose, mannitol and sorbitol. Each of these materials offers its own advantages for certain uses, but as with lactose and sucrose, binders and/or lubricants along with controlled granulation are normally needed.
Direct compression, in which a simple mix of dry ingredients is compressed without further treatment, is a desirable alternative to procedures involving wet or dry granulation of an ingredient mixture. Nevertheless, as is explained, for example, in U.S. Pat. No. 3,627,583 to Troy and No. 3,639,169 to Broeg, the direct compression technique has been of limited applicability.
The principal problem with direct compression was the lack of a suitable vehicle. As is explained in the Troy and Broeg Patents, the vehicle has to meet various criteria, and the previously suggested materials such as lactose, dicalcium phosphate or microcrystalline cellulose all have failings.
A similar point is made in U.S. Pat. No. 3,961,004 to Nasir, where criticism is also given of the suggested use of mannitol or sorbitol as direct compression materials.
In turn, the U.S. patents to Troy and to Broeg each put forward a multi-component material which is manufactured by a special procedure to give a pre-prepared direct compression vehicle. Thus, U.S. Pat. No. 3,627,583 prepares certain sugar agglomerates using specific amounts of carefully defined ingredients and snowballing of the mixture to give agglomerates. It will be seen that this treatment to form agglomerates is tantamount to a granulation step before incorporation of the active ingredient. The prepared agglomerate is a direct compression vehicle, but the vehicle is a specially produced version of the sugar which is present.
In U.S. Pat. No. 3,693,169, a compaction aid is pre-prepared by compacting a dry mix to give a compact, nonfriable sheet and breaking up the sheet. In this way a direct compression vehicle is made for subsequent compression together with an active ingredient, but it is again the case that the vehicle is a specially produced version of the carrier material.
More generally, it is to be noted that direct compression vehicles have invariably comprised specially prepared versions of diluent or carrier compounds, the compounds usually being admixed with various additives or aids as part of the preparation of the direct compression vehicle.